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Inflammation from belly fat may be linked to the early stages of Alzheimer’s disease decades before symptoms appear, a new study suggests.
“We’ve known for some time that the larger the abdomen, the smaller the memory centers in the brain,” said Dr. Richard Isaacson, an Alzheimer’s researcher and preventive neurologist at the Florida Neurodegenerative Disease Institute.
“This study shows a brain imaging sign of neuroinflammation that I haven’t seen before,” said Isaacson, who was not involved in the new study. “Brain imaging links abdominal fat, or visceral fat, to brain dysfunction through an inflammatory cascade.”
The study found that people in their 40s and 50s who had a greater amount of hidden belly fat “had a greater amount of an abnormal protein called amyloid in a part of the brain that we know is one of the oldest places where Alzheimer’s disease occurs.” Senior author Dr. Cyrus Raji, associate professor of radiology at Washington University School of Medicine in St. Louis.
Beta-amyloid plaques in the brain are one of the hallmarks of Alzheimer’s disease, along with tangles of a protein called tau. Amyloid plaques usually appear first, and tau tangles arrive later as the disease progresses.
“There is a gender difference as well, with men having a higher association between belly fat and amyloid than women,” Raji said. “The important reason is that men have more visceral fat than women.”
The study also found a relationship between deep belly fat and brain atrophy, or wasting of gray matter, in a part of the brain’s memory center called the hippocampus.
“This is important because brain atrophy is another biomarker for Alzheimer’s disease,” Raji said.
The gray matter in the brain contains the majority of brain cells that tell the body what to do. White matter is composed of fibres, usually distributed in bundles called tracts, which form connections between brain cells and the rest of the nervous system.
“We also found that individuals with greater amounts of visceral fat tend to have more inflammation in the circulating white matter pathways in the brain,” said lead author Dr. Mahsa Dolatshahi, a postdoctoral research fellow at the University of Washington School of Medicine.
Without a functional white matter highway, the brain cannot communicate appropriately with different parts of the brain and body.
Published as a pilot study in the Journal of Aging and Disease in August, Raji and his team originally imaged the brains and stomachs of 32 adults aged 40 to 60 years. The team has continued to add participants and now provides information on an additional 20 people – 52 people. the total — At the 2023 Radiological Society of North America conference on Monday.
As more people were added to the study, the details of how inflammation caused by belly fat affects the parts of the brain where Alzheimer’s disease arises have come into focus. Raji said the brain changes they discovered were modest but significant.
“The reason we see very subtle effects is because we are looking at middle age — people in their 40s and 50s — whereas previous studies looked at people in their 60s and 70s,” he said. “These are people who if they get Alzheimer’s, it won’t happen for another 20 or 25 years.
“So, we’re really exploring how early we can detect some of the subtle types of abnormalities that could be associated with Alzheimer’s disease,” Raji added. “By identifying this disease association of visceral fat, there are ways we can intervene in this population.”
Visceral fat and inflammation
When we think of fat, most of us think of subcutaneous fat, the kind that can be pinched under your skin or along your waistline. Subcutaneous fat typically makes up 90% of the body, according to the Cleveland Clinic.
Visceral fat cannot be pricked, prodded or pinched. Visceral fat hides behind the abdominal muscles, deep in the abdomen, and wraps around vital organs. Both types secrete hormones and other molecules, but experts say visceral fat is more metabolically active, sending signals that can lead to insulin resistance and other health problems.
“Subcutaneous fat is not usually associated with insulin resistance,” Isaacson said. “But the higher the level of visceral fat, the more resistant a person is to insulin, which causes inflammation in the body and brain.”
Insulin resistance occurs when the body’s cells do not respond well to insulin, a hormone needed to regulate blood sugar levels. This condition often leads to diabetes and a host of other chronic diseases.
“We hypothesized that inflammation in fat cells leads to insulin resistance, and this is accelerated by visceral fat,” Isaacson said. “Insulin resistance then causes inflammation that leads to rapid deposition of amyloid, one of the main signs of Alzheimer’s disease. That’s why people with diabetes are twice as likely to develop Alzheimer’s disease.”
MRI scans and expensive full-body scans are the most accurate way to measure visceral fat, but many use estimates based on waist circumference or waist size in proportion to height. To measure your waist, the Cleveland Clinic recommends wrapping a flexible tape measure around your waist just above your hips.
“For women, 35 inches (89 cm) or more means you are at risk for health problems caused by visceral fat. For men, the number is 40 inches (102 cm) or more,” the clinic says on its website.
“Regardless of weight, people should know if they have hidden visceral fat,” Raji said. “It can be completely missed using body mass index (BMI) or weight on the scale.”
This is because even thin people can have excess visceral fat. It’s called “skinny fat” or “TOFI” (thin on the outside, fat on the inside), and it can occur when a person exercises but has a poor diet, and in certain ethnic groups. Asians, for example, have more visceral fat than blacks, whites, or Hispanics.
There’s good news: Visceral fat responds well to diet and exercise, Raji said. “It is easier to lose visceral fat from diet and exercise than from subcutaneous fat because visceral fat is metabolized and burned more easily.”
There are many things that can target body fat, both from an exercise and nutrition perspective, Isaacson said.
“Eat a healthy diet and exercise regularly, which should include muscle strength training several times a week, along with fat burning and less intense cardio exercises for 45 to 60 minutes, several times a week,” he said.
More tips: Eliminate or reduce ultra-processed foods, reduce portion sizes, replace sugary drinks with water, limit processed meats, and limit high-fat meats and dairy products, such as cheese and butter, which are full of saturated fat, other experts suggest.
Watch your alcohol intake, too: It’s not just beer that leads to “beer belly,” according to the Mayo Clinic. Drinking alcohol of any kind will increase your waist circumference.
Pay attention to your sleep, too. Millions of Americans suffer from sleep deprivation on a daily basis, but studies have found that people who sleep less than six hours a day have higher levels of amyloid in their brains.
